MJML Email Preview — Test Gmail, Outlook & Mobile Before Sending

Paste your MJML above and MailViewr compiles it to HTML right in your browser, then renders it across Gmail, Outlook, Apple Mail and mobile — including dark mode. Free, no signup.

Open the full-screen MJML editor

Everything you need to preview MJML

The official MJML compiler turns MJML into HTML. MailViewr does that and everything after — previewing, testing and QA across real email clients, all in one place.

Compile MJML to HTML

Browser-side compilation with the official MJML engine — no install, no signup.

Gmail preview

See your compiled MJML in Gmail web, iOS and Android.

Outlook preview

Catch Word-engine quirks before you send.

Apple Mail & mobile

Preview macOS, iOS and mobile clients side by side.

Dark mode preview

Test how your MJML renders in Gmail and Apple Mail dark mode.

Pre-Send QA report

Run structural checks and a SpamAssassin score on the compiled HTML.

Download HTML

Export the generated, email-ready HTML for any ESP.

CSS compatibility

Get per-client compatibility scoring on the output.

Supported MJML components

MailViewr previews emails built from the full MJML component set, including:

<mj-section><mj-column><mj-button><mj-image><mj-text><mj-social><mj-table><mj-navbar><mj-carousel><mj-wrapper><mj-group><mj-divider><mj-spacer><mj-hero><mj-accordion><mj-raw>

From MJML to a rendered email

Write concise MJML, compile to responsive HTML, and preview how it actually renders.

Your MJML

<mjml>
  <mj-body>
    <mj-section>
      <mj-column>
        <mj-text font-size="20px">Welcome aboard 🎉</mj-text>
        <mj-button href="https://example.com">Get started</mj-button>
      </mj-column>
    </mj-section>
  </mj-body>
</mjml>

What you get

Responsive, Outlook-safe HTML
  → previewed in Gmail, Outlook,
    Apple Mail & mobile
  → dark mode tested
  → QA report + downloadable HTML

MJML vs HTML

MJML compiles to HTML, so you get responsive, Outlook-safe markup with far less code. MailViewr supports both — paste either and preview across clients.

Aspect	MJML	Hand-written HTML
Responsiveness	Automatic, mobile-first	Manual media queries
Outlook support	Generated table markup, Word-safe	You write the VML/conditionals
Maintainability	Concise, component-based	Verbose, nested tables
Development speed	Fast — fewer lines	Slower — more boilerplate
Output	Compiles to HTML	Already HTML

MJML preview FAQ

Can I preview MJML emails online?

Yes. Paste your MJML into MailViewr and it compiles to HTML in your browser, then renders across Gmail, Outlook, Apple Mail, Yahoo and mobile devices — including dark mode — so you can see exactly how it looks before sending.

Does MailViewr convert MJML to HTML?

It does. MailViewr compiles MJML to email-ready HTML in the browser using the official MJML engine. You can preview the result, run a QA report, and download the generated HTML for any ESP.

Can I test MJML in Outlook?

Yes. After compiling your MJML, MailViewr previews the HTML in Outlook (desktop and mobile) alongside Gmail and Apple Mail, so you can catch Word-engine rendering issues before you send.

Is the MJML compiler free?

Completely free, with no signup or install. Open the editor, paste your MJML, and preview instantly.

Is my MJML uploaded or stored?

No. MJML is compiled entirely in your browser. Your source is never uploaded to a server just to preview it.

MJML vs HTML — which should I use?

MJML is faster to write and produces responsive, Outlook-safe HTML automatically, which is ideal for new builds. Hand-written HTML gives you the most control. MailViewr supports both — paste either and preview across clients.